Field of the Invention
The invention relates to a method for the active damping of combustion oscillation in a combustion chamber and to a corresponding combustion apparatus.
An article entitled "Aktive Dampfung selbsterregter Brennkammerschwingungen (AIC) bei Druckzerstauberbrennern durch Modulation der flussigen Brennstoffzufuhr" [Active Damping of Self-Excited Combustion-Chamber Oscillations (AIC) in Pressure Atomizer Burners by Modulating the Liquid Fuel Supply] by J. Herrmann, D. Vortmeyer and S. Glei.beta., in VDI Reports No. 1090, 1993, describes how combustion oscillation occurs in a combustion chamber and how it can be actively damped. During combustion, in a combustion chamber, for example of a turbine, self-excited combustion oscillation may occur, which is also referred to as combustion instability. Such combustion oscillation arises as a result of interaction between a fluctuating release of power during combustion and acoustics of the combustion chamber. Combustion oscillation is often accompanied by high noise emission and mechanical load on the combustion chamber, which may lead to structural parts being destroyed. Active damping of combustion oscillation is achieved by modulation through the use of an actuating member (piezoelectric actuator). The actuating member modulates a fuel quantity which is supplied to a burner. A microphone records the acoustic oscillations in the combustion chamber. A regulating signal for regulating the modulation of the fuel quantity being supplied is derived from a microphone signal in such a way that the modulation of the fuel quantity being supplied takes place anti-cyclically to the combustion oscillation.
International Publication No. WO93/10401 has disclosed a burner configuration with two burners in a common combustion chamber. Each of the burners can be supplied with fuel through a fuel line. An acoustically acting element is coupled to a fuel line. It is preferably a passive element, in the form of a Helmholtz resonator, for example, which modifies the acoustic properties of the fuel line, i.e. which acoustically detunes the fuel line. In another configuration, the acoustically acting element is a loudspeaker which acts on fuel flowing through the fuel line. According to the single embodiment disclosed, the loudspeaker is driven through the use of a microphone disposed outside the combustion chamber.